The electronic properties of anatase titanium dioxide TiO${}_2$ thin films epitaxially grown on LaAlO${}_3$ substrates were investigated by synchrotron-X-ray spectroscopies (XAS, XPS and ARPES) and Infrared Spectroscopy. The Ti${}^{3+}$ fraction in TiO${}_{2-x}$ was varied by either changing the oxygen deposition pressure or by post-growth annealing in ultra-high-vacuum (UHV). Structural investigation of TiO${}_2$ thin films provide evidence of highly uniform crystallographic order for both as-grown and in-situ UHV annealed samples. Increasing amount of Ti${}^{3+}$ as a consequence of UHV annealing was calibrated by both in-situ XPS and XAS analysis. As-grown TiO${}_2$ samples, with low Ti${}^{3+}$ concentration, show distinct electron properties with respect to annealed films: namely, an absorption in the mid-infrared (MIR) region correlated to polarons formation and another peak in the visible range at 1.6,eV, correlated to the presence of localized defect-states (DS). With the increasing level of Ti${}^{3+}$ induced by post-annealing process, the MIR peak disappears while the DS peak red-shifts to the near-infrared region at about 1.0,eV. These results indicate the possibility of tailoring the optical absorption of anatase TiO${}_2$ films from visible towards the near-infrared regions.

中文翻译：

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在整个可见光到近红外光谱范围内调节锐钛矿薄膜的光吸收

锐钛矿型二氧化钛TiO的电子性能${}_2$ 在LaAlO上外延生长的薄膜${}_3$通过同步加速器X射线光谱仪（XAS，XPS和ARPES）和红外光谱对底物进行了研究。钛${}^{3+}$ TiO中的分数${}_{2-X}$通过改变氧气沉积压力或在超高真空（UHV）中通过生长后退火来改变合金的含量。TiO的结构研究${}_2$薄膜为生长和原位UHV退火样品提供了高度均匀的晶体学顺序的证据。钛的增加${}^{3+}$由于特高压退火的结果，已通过原位XPS和XAS分析进行了校准。生长的TiO${}_2$ 样品，低钛${}^{3+}$浓度显示出与退火膜有关的独特电子特性：即，在中红外（MIR）区域的吸收与极化子的形成有关，在可见光范围内的另一个峰值在1.6ev，与局部缺陷态的存在有关（DS）。随着钛含量的增加${}^{3+}$在后退火过程中，MIR峰消失，而DS峰在约1.0 eV处红移至近红外区域。这些结果表明有可能调整锐钛矿型TiO的光吸收${}_2$ 从可见光到近红外区域的胶片。